This invention relates to methods and apparatus for the formation of images as prints on objective bodies through transfer of images preformed by the sublimation transfer technique, and more specifically it relates to such systems as adapted for the formation of images on any selected objective body, such as cards, clothes, papers, and transparent sheets, although these are not limitative to the present invention.
Reliance is made generally upon the normal printing technique for formation of images on objective bodies. For the execution of the printing technique, provision and use of printing plates (forms or blocks) are requisite. No matter how simple the image-printing is, the plate-making is a very time-consuming the laborious procedure. This is much more so in the printing of various and complexed image combinations, such as those of graphic or portrait images combined with characters, letters or barcodes, as an example, representing extremely complicated and troublesome work.
Further, in the normal printing operation, various operating conditions, including ink selection and the like, must be carefully considered, depending upon the kind and nature of the printing object, thus the best selection thereof is highly delicate and not as simple as expected.
The present invention is proposed upon careful consideration of the foregoing facts, and an object of the invention is to provide a unique process for the formation of sharp and clear images regardless of the kind and nature of the object to be printed upon, and usable and effective materials and apparatuses for carrying out this unique process.
The method of thermal image transfer (sublimation image transfer) on clothes or fabrics with the use of thermal transfer dyestuffs has been practiced for a long time. In this conventional process, a dyestuff picture layer carrying thermal transfer dyestuff is formed on a substrate sheet which is then subjected to heat in an overlapped state on a cloth or fabric, the dyestuff thereby being transferred thermally onto the latter for forming the desired images thereon. By utilizing this technique, and with recent development of the image forming technology concerning fine thermal printers and the like, various fine image forming processes have been proposed to provide fine images which are comparable to photographic images and are transferred onto plastic films from thermal transfer sheets carrying thermal transfer dyestuffs.
According to these recently proposed processes, various images of cameras, or TVs, graphic images of personal computers and the like can be reproduced-easily in the form of hard copies on the surface of a transferred material such-as a paper or the like sheet carrying thereon a fixedly attached layer of polyester resin, as an example. These images thus reproduced represent an amply high level comparable to those obtained by photography or fine printing arts.
The thermal transfer process so far set forth has an advantage in that it can form any image in a convenient manner yet entails a problem in that it is limited to image-transferred products preferably of polyester and the like materials which must be dyed with thermal transfer dyes. On the other hand, the image-transferred products must be limited to specifically selected shapes, preferably film, sheet or the like configuration, and thus, such materials as wood, metal, glass or ceramics cannot be formed with images in this way. Further, even if the material is plastics such as polyester or the like, and when the image-forming surface is curved or undulated, or physical body other than sheet, even if it represents a plane surface, it is almost impossible to reproduce images precisely thereon, which naturally constitutes a grave problem in the art.
With recent development and enlargement of utilizing fields of various card-style products, such as cash-cards, telephone-cards, prepayment cards; and ID-cards, there are increasing demands for providing these cards with images, symbols and codes, so as to give various other functional and/or decorative effects. Moot of these cards are of planar form, but they are frequently not pliable and/or have uneven rough portions due to provision of characters and symbols, resulting in great difficulty in the scheduled image formation relying upon the thermal image transfer process.
There is therefore an urgent demand among those skilled in the art for the provision of a unique technique capable of forming sharp and clear images of desired patterns on the surface of an objective body of any preferred kind of material and having any shape and configuration and surface condition of any kind, and indeed, for combining and unifying image- and decoration effects.
The present invention is basically based on such a principle that a first image transfer pattern is formed on an image transfer material, preferably an image-transferable sheet, and in the form of dyestuff images through the sublimation image transfer process executed by first image transfer means, depending upon given image data, preferably including those of letters, characters, symbols, line images, graduated graphic representations, and then the first transfer pattern is transferred to second transfer means for retransferring the images onto an objective body so as to provide a final product.
Based upon the image data fed from various image data input means and at the first image-transfer means, a thermal head is actuated to execute printing operation through a dyestuff film (thermal image-transfer sheet) on an image-transfer material (or more specifically on an image-transferable material which means an image-transferable sheet. This image-printing is carried out according to the sublimation or sublimative image transfer technique. Thus, in this case, the dyestuff on the dyestuff film is transferred or shifted under the influence of heat energy from the thermal head onto the image-transferable material through sublimation, thus providing the first image-transferred means. Since this first image-transferred means has been thus formed with the images by the sublimated dyestuff, they are, then, transferred onto the second image-transferable means which will be brought into tight contact with the object to be decorated and subjected to heat and pressure for execution of further image-transfer operation to provide the final desired product.
In the present invention, the image-transfer material (image-transferable sheet) is, as above referred to, formed with images by the sublimative image transfer technique for providing first image-transfer means which has highly sharp and clear images as the operation and results of the characterizing feature of the sublimation image-transfer technique. Therefore, because of the transfer of such sharp and clear images onto the object, it becomes possible to form the images thereon, and indeed, practically irrespective of the kind and nature of the object. In this way, thus, fine image-formation is assured onto practically any objective substance.
And further, by execution of control of the thermal energy applied during the sublimative image-transfer step, the resulting color effect is superior and the image quality is good.
The images sublimatingly applied and formed in the foregoing way are subjected to a further transfer, and onto a substrate product, for providing a final decorative product as desired. In this final product, it should be noted that the underlying layer underneath the images during the sublimative image-transfer stage appears now at the top, acting thus as a kind of protecting layer upon up-and-down positional conversion during execution of the second and final image-transfer stage, resulting in realization of various and numerous effects. As an example, attainment of substantial reduction of contamination, improvement of light resistance, weather resistance and chemical resistance; substantial reduction of color fading; provision of glazing effect; easier and simpler introduction of granular and/or undulated image appearance.
The inventive process is carried into effect basically in such a manner that an image-reception layer provided on one surface of an image-transferable sheet is subjected to an image-forming step with the use of dyestuff capable of depositing therein depending upon the fed image data, so as to form the required images, and then, the image-reception layer of the image-transferable sheet, having been image-fixed and thus now image-carrying, is stuck onto the surface of the object to be decorated upon.
As for the image-transferable sheet adapted for use in the image-transfer during execution of the inventive process, it consists basically of a sheet-like substrate and a reception layer attached, however, in a separable manner, onto one surface thereof. As a modification of the inventive process from the basic mode set forth above, the sheet-like substrate is caused to remain, even after completion of the image-transfer step, as may be occasionally required. In this modified case, it is unnecessary to make the image-reception layer of the image-transfer sheet separable.
Under occasion, the inventive process may be brought into effect in such a way that the image-reception layer of the image-transfer sheet is transferred upon execution of the image-forming step, and indeed, once onto an intermediate image-transfer substrate which is then retransferred, together with the once transferred image-reception layer, onto the surface of an object to be decorated on, and thus, in a retransferring manner.